The subject of renewable energy development has attracted worldwide attention. In particular, the solar energy industry is developing very rapidly. On one hand, the emphasis is put on reducing the fabrication cost of solar cells. On the other hand, endeavors are devoted to optimizing the utilization of solar energy as well as the conversion efficiency of solar cells. Popularization of solar energy is being promoted.
Solar cells can be classified into silicon, compound, and organic solar cells. In compound solar cells, the III-V compound solar cells, which include the III-V compounds gallium arsenide (GaAs), indium gallium arsenide (InGaAs), and indium gallium phosphide (InGaP), have the highest conversion efficiency. Presently, III-V compounds with different materials have been stacked to form multi junction solar cells with an extended absorption spectrum of the sunlight. Compared with silicon solar cells, the conversion efficiency of solar energy is improved significantly.
III-V solar cells occupy smaller area and have higher conversion efficiency. By assembling with a concentrating lens, a concentrator photovoltaic module can be given. By using the concentrating lens, the sunlight is concentrated on the solar cells with a small area for generating power and increasing the power generating efficiency. A concentrator photovoltaic module mainly comprises a concentrating lens, a solar cell, a circuit board, and a module frame. The solar cell is combined with the circuit board and is called the receiver. In general, a Fresnel lens with 1000-times concentration is adopted. Nonetheless, because the focal point of the concentrating lens has to fall on the solar cells before the concentrator photovoltaic module can concentrate light, a sun tracker should be used to drive the module to orient to the direction of the sun.
In addition, during the presses of assembling the concentrator photovoltaic module, precise optical alignment must be adopted for focusing the sunlight on the solar cells and ensuring power generating efficiency. Considering deflection occurs when the light passes through the concentrating lens, an optically inactive region is disposed on the concentrating lens according to the prior art. It means that a region without the concentrating lens is reserved. When the light passes through the optically inactive region, no reflection occurs. Instead, the light will illuminate on the circuit board perpendicularly. Then, by moving the circuit board, a laser spot is aimed at an optical alignment point and thus completing optical alignment of the module. Although optical alignment can be performed effectively, the sunlight incident to the optically inactive region cannot be reflected to the solar cells for generating power, resulting in waste of the solar energy.
In order to expand the area of a concentrator photovoltaic module for receiving the sunlight and fully utilizing the solar energy by increasing the output power performance of the photovoltaic module, a novel optical alignment method and device should be developed for replacing the optically inactive region.